The present invention relates to a valve prosthesis to be put into place by an endoluminal approach. The prosthesis is the type comprising a flexible shutter and an annular carrier structure that is radially rigid and suitable for being surgically implanted at the location of a heart valve.
The heart comprises two atriums and two ventricles which are separated by valves. Valves are also present at the outlets from the right ventricle (pulmonary valve) and from the left ventricle (aortic valve).
These valves ensure that blood flows in one direction only, avoiding reflux of blood at the end of ventricular contraction.
Valves can suffer diseases. In particular, they can suffer from poor opening, thus reducing the flow of blood, or from being somewhat leaky, thus allowing a reflux or regurgitation of blood back into the ventricle that has just expelled it.
These regurgitation problems lead to abnormal expansion of the ventricle thereby producing, in the long run, heart failure.
It is known to treat that type of disease surgically, by replacing the diseased valve. Diseased valves, and in particular the aortic valve at the outlet from the left ventricle, are replaced by valves taken from a deceased subject, or by prosthetic valves, commonly referred to as bioprostheses. A prosthetic valve is constituted by a metal ring structure and a flexible shutter made of tissue of animal origin. The shutter is permanently secured to the structure.
Such valves are described in particular in documents WO 01/03095 and WO 00/27975.
Once implanted, the structure bears against the inside wall of the heart to which it is sutured, in particular at the inlet to the aortic valve coming from the left ventricle.
It is found that after such a prosthesis has been implanted for several years, it degenerates and no longer functions efficiently. In particular, the flexible shutter tears and presents holes, or the shutter becomes calcified and thus loses flexibility, thus no longer being capable of deforming to perform its valve function. It is then necessary to put a new prosthesis into place.
However, it is not possible to remove the old prosthesis via an endoluminal path, in particular because the carrier structure of the prosthesis is sutured to the wall of the heart, meaning that they cannot be separated without major surgery for complete replacement of the valve.
In order to avoid a major surgical operation for removing the old prosthesis and putting a second prosthesis into place, it has been envisaged that a new prosthetic valve could be put into place by an endoluminal approach inside the old prosthesis which is left in place.
The new prosthetic valve is formed by a tubular support constituted by a radially deformable lattice fitted with a flexible shutter disposed in the duct defined by the tubular support. The shutter is connected to the tubular support and presents a shape that enables it, by deforming, to allow blood to flow in one direction and to prevent the blood from flowing in the opposite direction.
It has been envisaged that the tubular support could be made of interlaced resilient metal wires defining meshes that are generally lozenge-shaped. Such a tubular support is known as a “stent”. The tubular support is deformable between an insertion position, in which its diameter is reduced, and an implantation position in which its diameter is larger and sufficient to enable the support to bear against the inside of the carrier structure of the old prosthesis.
In order to be put into place, such prosthetic valves comprising a tubular lattice support are disposed inside a small-diameter catheter. The end of the catheter is brought via the arterial network to the region where the no longer functioning, old prosthesis has been fitted. The new prosthetic valve is pushed out from the catheter using a wire-shaped member engaged in the catheter. Since the tubular support is resilient, it deploys immediately on its own when it is no longer compressed radially by the catheter. It then comes to bear around the inside perimeter of the carrier structure of the old prosthesis.
Putting the new valve into place and deploying it are operations that are very difficult, particularly when the old prosthesis is very damaged.